Maven: Force Jersey to use specific artifact version - maven

Question

I have a Maven repository where I load Jena TDB 0.9.3 (which depends on Jena ARQ 2.9.3), Jersey 1.8 and RMOnto 1.0. The point is, as you expected, to do some analysis on semantic datasets.
It looks like RMOnto has ARQ 2.8.7 built in, as in "hardwired". There isn't any explicit dependency in its pom file, yet the jar file contains a ARQ.class. It's very tricky because you won't notice it with Maven Enforcer Plugin and the like.
It looks like this causes Jersey to use RMOnto's ARQ version instead of the one defined in pom.xml. Here is a minimal example. When you run the test (checks whether or not ARQ.VERSION equals 2.9.3), it succeeds. When you build the project and deploy it on a Tomcat 7, you should see 2.8.7 as output.
Is this behaviour expected and why?
How could one force Jersey to use ARQ 2.9.3?
In case it's not possible, could one isolate RMOnto to use 2.8.7 while the rest of the source uses 2.9.3?
Thanks in advance!

Answer 1

You should define the ARQ 2.9.3 first in the dependencies list. By doing that you force your build to use that specific version. The dependency order is relevant when choosing what artifact to use.
Update
OK, I understand what the problem is.
The RMOnto jar is obviously shaded according to the pom: http://semantic.cs.put.poznan.pl/maven/put/semantic/RMOnto/1.0/RMOnto-1.0.pom.
Tomcat 7 loads the jars in WEB-INF/lib in an undefined order. This means that even if you define ARQ 2.9.3 to be first in your dependencies it will not be the case when the application is run in Tomcat. http://tomcat.apache.org/tomcat-7.0-doc/class-loader-howto.html
Good thing is that Tomcat always look in WEB-INF/classes before WEB-INF/lib for dependencies.
So what you can do as a work around is to make sure that the ARQ 2.9.3 version is added to the WEB-INF/classes folder. This can be done using the maven-dependency-plugin:
<build>
<plugins>
<plugin>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<phase>prepare-package</phase>
<goals>
<goal>unpack</goal>
</goals>
<configuration>
<artifactItems>
<artifactItem>
<groupId>org.apache.jena</groupId>
<artifactId>jena-arq</artifactId>
<version>2.9.3</version>
<outputDirectory>${project.build.directory}/classes</outputDirectory>
<excludes>**/META-INF/</excludes>
</artifactItem>
</artifactItems>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
Your war as well as your exploded war will now contain all the classes from ARQ 2.9.3 in the WEB-INF/classes folder. They will be loaded before any jar-file that is in WEB-INF/lib folder.
NB: I have not tested this on Tomcat but I cannot see that it would not work.
NB2: This is a hack. Best thing would be to remove the ARQ packages out of the RMOnto jar.

Answer 2

You should file a defect report against RMOnto. Hard-wiring library code into a jar, instead of including it as a dependency you can manage in the POM, is definitely a bad idea that the code maintainer should fix.

Answer 3

If the files have been copied directly to the RMOnto .jar, the behaviour is expected.
In that case, I'd say the best bet is to hardcode it away, aka remove the ARQ files directly from the package. Opening up the RMOnto-1.0.jar package one can see arq files in the arq folder. What you'd need to do is open up the jar file (it's just a .zip), remove the ARQ files from there, store the edited RMOnto package in your version control / repository and refer to the edited package from there. Also, you'd need to add excludes statement to your pom for the old version of ARC and keep the dependency to the new version.
If you feel like it, it would be also good practice to remove the other dependencies that haven't been mentioned in the RMOnto's pom file, then add them in the RMOnto pom file (and rebuild, if you have the source code). This way Maven mechanism would be aware of them. The file seems to contain a lot of dependencies like this, which will cause headaches in the future.